A panel substrate, which is a component of a flat image display element such as a liquid crystal panel, is an electric circuit substrate having, on the inner surface, various electric circuit elements including pixel electrodes as individual units of image display, switching elements for applying certain voltages on pixel electrodes, and metal wiring.
Electrode terminals are disposed along the borders of the panel substrate of the liquid crystal panel, wherein the electrode terminals are drawn from the metal wiring formed over the image display region. Flexible printed circuits (FPC) are connected to these electrode terminals. Applied to the electrode terminals through the flexible printed circuits are various image display signals from peripheral circuit substrates and other components except the liquid crystal panel, as well as the power supply voltage required for the panel substrate to operate as an electric circuit substrate. Since the flexible printed circuits can be bent, the peripheral circuit substrate is bonded to the back of a bezel, a frame-like structural member with a bottom, in which the liquid crystal panel and the backlight are encased. This configuration constitutes a liquid crystal display device, which is an electric circuit structure.
The flexible printed circuit, which connects the panel substrate and the peripheral circuit substrate, includes a flexible base film having a particular wiring pattern on it. The wiring pattern is formed with metal foil (e.g., copper foil). Furthermore, the flexible printed circuit, together with the wiring pattern, is covered by an insulating protective layer. The flexible printed circuit is electrically connected to the panel substrate through an aperture in the base film that exposes the wiring pattern. Through the aperture, the wiring pattern makes direct contact with the electrode terminal on the panel substrate. Liquid crystal display devices also employ TCP (Tape Carrier Package), in which circuit elements such as driver semiconductor chips and capacitors that are connected to the wiring pattern are mounted on the flexible printed circuit.
For easy handling, in the case of TCP, flexible printed circuits having circuit elements such as semiconductor chips mounted therein are formed in multiples on a carrier tape so as to be individually separated for connection to the panel substrate by being punched out from the carrier tape in a predetermined shape by a metal cutter.
Patent Document 1 discloses a technology for forming a wiring pattern on a flexible printed circuit, wherein the lengths of individual wires on the flexible printed circuit alternate, having every other wire shorter, where the shorter wire does not extend to the punching line. According to this technology, a short-circuit failure caused by conductive foreign matter, i.e., a wire detachment from the base film triggered by the stress from the punching out process, can be prevented.    Patent Document 1: Japanese Utility Model Application Laid-Open Publication No. H4-28437